Current technology in the manufacturing of jewelry uses many different materials. Some jewelry has structural material as well as ornamental material, and in some jewelry materials are used which are both structural and decorative. As an example, men's and women's wedding bands, and other types of decorative rings made to fit the human fingers, are typically made out of three basic material categories. These categories are: metals and metal alloys, such as gold, silver, and platinum; natural occurring gemstone materials such as jade, hematite, and turquoise; and ceramics such as alumina; and recently even cemented tungsten carbide (often called tungsten). These rings often have gem stones or other materials affixed for ornamentation.
Jewelry types and material preferences tend to be influenced by current trends similar to clothing fashions. Recently, cemented tungsten carbide rings have come into vogue for men's wedding and decorative rings displacing somewhat the more traditional metal rings. The jewelry market tends to be receptive to new and unusual materials.
In the past, diamonds have been used as ornamentation on jewelry. Due to its expense, rarity, and difficulty to produce and process, it has not been used as a bulk material in rings or jewelry. Polycrystalline Diamond (PCD) is an engineered material mostly used for industrial drilling and machining. In jewelry, naturally occurring black carbonaceous diamond (sometimes called carbonado) has been cut into gem stones.
There are obstacles to using manufactured polycrystalline diamond in jewelry, including the available size and composition of the PCD. Fabricated PCD could be formed or cut into thin faces due to the limitations in thickness in which PCD is sintered (up to 0.200″) using current technology. These thin faces could then be mounted in rings, on cuff-links, and on necklace pendants, for example, but could not form the bulk of many pieces of jewelry such as rings because of the size limitations of the PCD. One further barrier to the use of PCD as a bulk jewelry material is that it is historically sintered in the presence of cobalt and/or nickel, which are both known to cause skin allergies, as well as having other problems with biocompatibility.